GS1559 Data Sheet
4.8 DVB-ASI Functionality
The GS1559 is said to be in DVB-ASI mode once the device has detected 32
consecutive DVB-ASI words without a single word or disparity error being
generated. The device will remain in DVB-ASI mode until 32 consecutive DVB-ASI
word or disparity errors are detected, or until SMPTE TRS ID words have been
detected.
The lock detect block may also drop out of DVB-ASI mode under the following
conditions:
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•
•
•
RESET_TRST is asserted LOW
CDx is HIGH
SMPTE_BYPASS is asserted HIGH in slave mode
DVB_ASI is asserted LOW in slave mode
K28.5 sync patterns in the received DVB-ASI data stream will be detected by the
device in either inverted or non-inverted form.
In master mode, the GS1559 sets the SMPTE_BYPASS pin LOW and the
DVB_ASI pin HIGH to indicate that it has locked to a DVB-ASI input data stream.
When operating in slave mode, the application layer must set the SD/HD pin HIGH,
in addition to setting SMPTE_BYPASS LOW and DVB_ASI HIGH, in order to
enable DVB-ASI operation.
4.8.1 DVB-ASI 8b/10b Decoding and Word Alignment
After serial-to-parallel conversion, the internal 10-bit data bus is fed to the DVB-ASI
8b/10b decode and word alignment block. The function of this block is to word align
the data to the K28.5 sync characters, and 8b/10b decode and bit-swap the data
to achieve bit alignment with the data outputs.
The extracted 8-bit data will be presented to DOUT[17:10], bypassing all internal
SMPTE mode data processing.
NOTE: When operating in DVB-ASI mode, DOUT[9:0] are forced LOW.
4.8.2 Status Signal Outputs
In DVB-ASI mode, the DOUT19 and DOUT18 pins will be configured as DVB-ASI
status signals SYNCOUT and WORDERR respectively.
SYNCOUT will be HIGH whenever a K28.5 sync character is present on the output.
This output may be used to drive the write enable signal of an external FIFO, thus
providing a means of removing the K28.5 sync characters from the data stream.
Parallel DVB-ASI data may then be clocked out of the FIFO at some rate less than
27MHz. See
WORDERR will be high whenever the device has detected a running disparity error
or illegal code word.
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July 2005
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GENNUM [ GENNUM CORPORATION ]
